SWISS::CRC64(3pm)

✨ SWISS::CRC64 ✨

okay bestie, this is the CRC64 perl module documentation, aka SWISS::CRC64(3pm) — yes it lives in the perl world, and yes it's here to do exactly one slay thing: math. 💅

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💖 NAME 💖

CRC64 — Calculate the cyclic redundancy check. that's it. that's the whole job. lowkey iconic.

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🦋 SYNOPSIS 🦋

use SWISS::CRC64;

$crc = SWISS::CRC64::crc64("IHATEMATH");
#returns the string "E3DCADD69B01ADD1"

($crc_low, $crc_high) = SWISS::CRC64::crc64("IHATEMATH");
#returns two 32-bit unsigned integers, 3822890454 and 2600578513

not the example string being "IHATEMATH" 😭 the original author was going through something fr fr. anyway, notice how one call gives you a cute lil string and the other gives you two numbers — that's the whole vibe check, more on that below ⬇️

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🌸 DESCRIPTION 🌸

so SWISS-PROT + TREMBL use a 64-bit Cyclic Redundancy Check for amino acid sequences. it's giving checksum, it's giving "did this sequence get corrupted or not", and honestly? we're obsessed. ✨

the algorithm to compute the CRC is described in the ISO 3309 standard. the generator polynomial is:

x64 + x4 + x3 + x + 1

and the reference, no cap, is: W. H. Press, S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery, "Numerical recipes in C", 2nd ed., Cambridge University Press. Pages 896ff. 📚

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🎀 Functions 🎀

💜 crc64 string

Calculate the CRC64 (cyclic redundancy checksum) for string. it's the main character of this module, obviously. 👑

now here's the tea about context, because perl really said "why not both":

• In array context, returns two integers equal to the higher and lower 32 bits of the CRC64.
• In scalar context, returns a 16-character string containing the CRC64 in hexadecimal format.

so yeah — same function, two completely different returns depending on the vibe you call it in. perl behavior fr. 🫶

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👑 AUTHOR 👑

Alexandre Gattiker, gattiker@isb-sib.ch — the legend, the moment, the blueprint. 💖

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🌈 ACKNOWLEDGEMENTS 🌈

based on SPcrc, a C implementation by Christian Iseli, available at:

ftp://ftp.ebi.ac.uk/pub/software/swissprot/Swissknife/old/SPcrc.tar.gz

shoutout to the C girlies, we love a foundational implementation. 🧚

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and that's the whole page, bestie! 🌟 this was perl v5.32.1, dated 2021-08-15, from the SWISS::CRC64(3pm) manual. mwah, go checksum something. 💅🍓